Microphone system with non-orthogonally mounted microphone die

ABSTRACT

A microphone system has a lid coupled with a base to form a package with an interior chamber. The package has a top, a bottom, and a plurality of sides, and at least one of those sides has a portion with a substantially planar surface forming an opening for receiving an acoustic signal. The microphone system also has a microphone die positioned within the interior chamber. The microphone is positioned at a non-orthogonal, non-zero angle with regard to the opening in the at least one side.

FIELD OF THE INVENTION

The invention generally relates to microphones and, more particularly,the invention relates to packages for microphones.

BACKGROUND OF THE INVENTION

MEMS microphones are used in a growing number of devices, such as mobiletelephones, laptop computers, voice recorders, hearing instruments, andother electronic devices. To those ends, MEMS microphone dies typicallyare mounted within a package interior and controlled by an adjacentintegrated circuit die. For example, a MEMS microphone package mayinclude a substrate, such as an FR-4 based printed circuit board (PCB),a MEMS microphone die attached to the substrate, and a cup-shaped lidattached to the substrate to create a package. The interior of thepackage forms an interior chamber that protects the fragile MEMSmicrophone die from the environment.

The interior chamber is not completely isolated, however, from theexternal environment. Specifically, the package also has an aperture topermit communication between the microphone die and an acoustic signalgenerated outside of the package. For example, to permit access of anacoustic signal into the package, the substrate may form a through-holeaperture under the microphone die. The acoustic signal thus entersthrough the aperture, and strikes the diaphragm portion of themicrophone die, causing the die to generate corresponding electricalsignals.

Ergonomic considerations of an underlying device (e.g., a hearinginstrument) often can cause the microphone aperture to be located in aregion or wall with very little clearance. The art has responded to thisby locating some microphone package apertures in the smaller side wallsof the package. Use of the side wall for the aperture, however, canproduce an undesirable acoustic path between the hole and the microphonedie.

SUMMARY OF VARIOUS EMBODIMENTS

In accordance with one embodiment of the invention, a microphone systemhas a lid coupled with a base to form a package with an interiorchamber. The package has a top, a bottom, and a plurality of sides, andat least one of those sides has a portion with a substantially planarsurface forming an opening for receiving an acoustic signal. Themicrophone system also has a microphone die positioned within theinterior chamber. The microphone is positioned at a non-orthogonal,non-zero angle with regard to the opening in the at least one side.

The microphone system also may have a ramped portion with a channelacoustically coupled with the opening. The ramped portion may have asecuring surface forming a non-orthogonal angle with regard to theopening. The microphone die preferably is secured to the securingsurface of the ramped portion, and the channel may acoustically couplethe opening and the microphone die. The channel further may have acontour configured to direct an acoustic signal in a direction that issubstantially orthogonal to the diaphragm of the microphone die.

Among other things, the system further may have a substrate secured withthe base. To control the microphone die, the substrate may support acircuit die, and a wire bond can electrically connect the microphone diewith the circuit die. Moreover, the base may have an interior face, withfirst and second portions, within the interior chamber. The noted secondportion of the base may form an obtuse angle with the first portion, andthe die may be secured to the second portion.

Some embodiments form at least one location protrusion on the baseadjacent to the lid. In addition or alternatively, to ensure sufficientfunctionality, the package may be configured to mitigate electromagneticinterference. For example, one or both of the base and lid can includeinjection molded material and conductive material to mitigateelectromagnetic interference. The ultimately formed package may beconfigured to be surface mountable, or mountable to an exterior circuitboard by some other means. In some embodiments, the microphone die maybe positioned at a non-orthogonal, non-zero angle with regard to aplurality of the external side faces of the package and/or thetop/bottom package faces.

In accordance with another embodiment of the invention, a microphonesystem has a lid coupled with a base that forms a package with aninterior chamber. The package has a plurality of exterior sides thattogether form a generally rectangular exterior shape. To provide signalaccess to the interior chamber, the package has an opening formedthrough one of its exterior sides. Specifically, the openingacoustically couples the interior chamber with the exterior of thepackage. The system also has a MEMS microphone die mounted within theinterior chamber at a non-orthogonal, non-zero angle to the opening.

In accordance with other embodiments of the invention, a method offorming a microphone system provides a base and a lid, and secures amicrophone die to one of the base and the lid. The method also securesthe base to the lid to form a package having an interior chambercontaining the microphone die. The package has a plurality of exteriorsides that together form a generally rectangular exterior shape, and atleast one of the plurality of exterior sides forms an opening forreceiving an acoustic signal into the interior chamber. The microphonedie is positioned within the interior chamber at a non-orthogonal,non-zero angle to at least one of the exterior sides.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art should more fully appreciate advantages ofvarious embodiments of the invention from the following “Description ofIllustrative Embodiments,” discussed with reference to the drawingssummarized immediately below.

FIGS. 1A-1D schematically show a plurality of different types of hearingaids that may incorporate illustrative embodiments of the invention.

FIG. 2 schematically shows one example of a cochlear implant that mayincorporate illustrative embodiments of the invention.

FIG. 3 schematically shows a perspective view of a packaged microphonethat may implement illustrative embodiments of the invention.

FIG. 4A schematically shows a perspective view of a MEMS microphone thatmay be used with illustrative embodiments of the invention.

FIG. 4B schematically shows a cross-sectional view of the MEMSmicrophone of FIG. 5A across line B-B.

FIG. 5A schematically shows the packaged microphone of FIG. 3 withoutits lid removed to show the internal components.

FIG. 5B schematically shows a perspective bottom view of the packagedmicrophone of FIG. 3.

FIG. 5C schematically shows a side view of the packaged microphone ofFIG. 3.

FIG. 5D schematically shows a cross-sectional view of the packagedmicrophone, focusing on the inlet port and channel leading to themicrophone die.

FIG. 6A schematically shows a perspective view of another embodiment ofthe invention.

FIG. 6B schematically shows the alternative embodiment of FIG. 6A withthe lid removed to show the internal components.

FIG. 7 shows a process of forming a packaged microphone, such as themicrophones shown in FIGS. 3 and 6A, in accordance with illustrativeembodiments of the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In illustrative embodiments, a packaged microphone has a microphone diemounted in a manner that delivers high-quality output signals while, atthe same time, permitting use with smaller package form factors (e.g.,within hearing instruments). To that end, the microphone die is mountedat an angle to its acoustic signal access port. This can havesignificant benefits in a wide variety of microphone types, includingside port microphones commonly used in hearing instruments. For example,this design aligns the microphone die to more favorably receive anincoming acoustic signal (i.e., at a more favorable strike angle), thusproducing an improved signal. Moreover, it may enlarge the back volume,thus further enhancing system performance. Details of illustrativeembodiments are discussed below.

FIGS. 1A-1D illustratively show various different types of hearing aids10A that may incorporate microphone systems implementing illustrativeembodiments of the invention. FIGS. 1A and 1B show different “behind theear” types of hearing aids 10A that, as their name suggests, have asignificant portion secured behind a person's ear during use. Incontrast, FIGS. 1C and 1D show hearing aids 10A that do not have acomponent behind the ear. Instead, these types of hearing aids 10A mountwithin the ear. Specifically, FIG. 1C shows an “in-the-ear” hearing aid10A which, as its name suggests, mounts in-the-ear, while FIG. 1D showsan “in-the-canal” hearing aid 10A which, as its name suggests, mountsmore deeply in the ear—namely, in the ear canal.

With reference to FIG. 1A, the intelligence, sensors (e.g., microphonesystems 17, discussed in greater detail below with regard to FIGS. 3-7),and logic of the behind the ear type of hearing aid 10A lies primarilywithin a housing 12A that mounts behind the ear. To that end, thehousing 12A forms an interior that contains internal electronics forprocessing audio signals, a battery compartment 14 (a powering module)for containing a battery (not shown) that powers the hearing aid 10A,and mechanical controlling features 16, such as knobs, for controllingthe internal electronics. In addition, the hearing aid 10A also includesa microphone system 17 (e.g., including a packaged microphone die, alsoreferred to using reference number 17) for receiving audio signals, anda speaker 18 for transmitting amplified audio signals received by thepackaged microphone 17 and processed by the internal electronics. Ahollow tube 20 directly connected to the end of the hearing aid 10A,right near the speaker 18, channels these amplified signals into theear. To maintain the position of this tube 20 and mitigate undesiredfeedback, the hearing aid 10A also may include an ear mold 22 (also partof the body of the hearing aid 10A) formed from soft, flexible siliconemolded to the shape of the ear opening.

Among other things, the hearing aid 10A may have circuitry and logic foroptimizing the signal generated through the speaker 18. Morespecifically, the hearing aid 10A may have certain program modes thatoptimize signal processing in different environments. For example, thislogic may include filtering systems that produce the following programs:

-   -   normal conversation in a quiet environment,    -   normal conversation in a noisy environment,    -   listening to a movie in a theater, and    -   listening to music in a small area.

The hearing aid 10A also may be programmed for the hearing loss of aspecific user/patient. It thus may be programmed to provide customizedamplification at specific frequencies. Some of this functionality can beimplemented within its internal microphone system 17.

The other two types of hearing aids 10A typically have the same internalcomponents, but in a smaller package. Specifically, the in-the-earhearing aid 10A of FIG. 1C has a flexible housing 12A, with the notedinternal components, molded to the shape of the ear opening. Inparticular, among other things, those components include a microphone 17facing outwardly for receiving audio signals, a speaker (not shown)facing inwardly for transmitting those signals into the ear, andinternal logic for amplifying and controlling performance.

The in-the-canal hearing aid 10A of FIG. 1D typically has all the samecomponents, but in a smaller package to fit in the ear canal. Somein-the-canal hearing aids 10A also have an extension (e.g., a wire)extending out of the ear to facilitate hearing aid removal. Because theyfit in tight spots (e.g., behind the ear or in the ear canal), space forinternal system components (e.g., microphones) is at a premium.

FIG. 2 schematically shows another type of hearing instrument, acochlear implant 10B, which, in a similar manner, also has significantspace constraints for its internal components. At a high level, acochlear implant 10B has the same function as that of a hearing aid 10A;namely, to help a person hear normally audible sounds. A cochlearimplant 10B, however, performs its function in a different manner byhaving an external portion 24 that receives and processes signals, andan implanted portion 26 physically located within a person's head.

To those ends, the external portion 24 of the cochlear implant 10B has abehind the ear portion with many of the same components as those in ahearing aid 10A behind the ear portion. The larger drawing in FIG. 2shows this behind the ear portion as a transparent member since the earcovers it, while the smaller drawing of that same figure shows it behindthe ear.

Specifically, the behind the ear portion includes a housing/body 12Bthat contains a microphone 17 for receiving audio signals, internalelectronics for processing the received audio signals, a battery, andmechanical controlling features 16 (e.g., knobs) for controlling theinternal electronics. Those skilled in the art often refer to thisportion as the “sound processor” or “speech processor.” A wire 19extending from the sound processor connects with a transmitter 30magnetically held to the exterior of a person's head. The speechprocessor communicates with the transmitter 30 via the wire 19.

The transmitter 30 includes a body having a magnet that interacts withthe noted implanted metal portion 26 to secure it to the head, wirelesstransmission electronics to communicate with the implanted portion 26,and a coil to power the implanted portion 26 (discussed below).Accordingly, the packaged microphone 17 in the sound processor receivesaudio signals, and transmits them in electronic form to the transmitter30 through the wire 19, which subsequently wirelessly transmits thosesignals to the implanted portion 26.

The implanted portion 26 thus has a receiver with a microprocessor toreceive compressed data from the external transmitter 30, a magnethaving an opposite polarity to that in the transmitter 30 both to holdthe transmitter 30 to the person's head and align the coils within theexternal portion 24/transmitter 30, and a coil that cooperates with thecoil in the exterior transmitter 30. The coil in the implanted portion26 forms a transformer with the coil of the external transmitter 30 topower its own electronics. A bundle of wires 32 extending from theimplanted portion 26 passes into the ear canal and terminates at anelectrode array 34 mounted within the cochlea 35. As known by thoseskilled in the art, the receiver transmits signals to the electrodearray 34 to directly stimulate the auditory nerve 36, thus enabling theperson to hear sounds in the audible range of human hearing.

Indeed, illustrative embodiments of the invention may implementmicrophone systems 17 in a variety of other underlying devices. Forexample, among other things, the microphone systems 17 discussed hereinmay be implemented in mobile telephones, smartphones, cameras,computers, gaming systems, and hand-held public announcement (“PA”)devices. Accordingly, discussion of hearing instruments or some otherhigher level system is for exemplary purposes only and not intended tolimit all embodiments of the invention.

FIG. 3 schematically shows a packaged microphone system 17 (as notedabove, also referred to as a “microphone system 17” or “packagedmicrophone 17”) implemented in accordance with illustrative embodimentsof the invention. The packaged microphone 17 has a package 38 that maybe coupled with an underlying apparatus, such as a printed circuit boardwithin a hearing instrument 10A or 10B or mobile telephone. Theunderlying apparatus, however, can have any of a variety of otherdevices (e.g., other integrated circuits). Accordingly, discussion of aprinted circuit board is illustrative and not intended to limit avariety of other embodiments.

The package 38 has a base 40 that, together with a corresponding lid 42,forms an interior chamber 43 containing at least two dies that togetherreceive and process incoming acoustic signals. To form the chamber 43,the lid 42 has four side walls 44 extending downwardly from asubstantially planar top surface 46. In a corresponding manner, the base40 has a generally planar bottom surface 48 with a specially configuredtop surface as discussed below. One of the sidewalls of the lid 42 has aspecially shaped contour to receive a complementary upwardly extendingportion 52 of the base 40. That upwardly extending portion 52 of thebase 40 forms an audio input port 54 (also referred to as an aperture54, opening 54 or inlet port 54) that enables ingress of audio/acousticsignals into the chamber 43.

The interior chamber 43 contains a microelectromechanical systemmicrophone die 56 (not shown in this figure, but discussed in detailbelow with regard to FIGS. 4A and 4B, also known as a “MEMS microphone”or “silicon microphone”) for receiving and converting incoming acousticsignals into electronic signals, and a circuit die 58 (also not shown inthis figure, but discussed with regard to FIG. 5A) for controlling andprocessing signals within the system 17. After it is converted into anelectrical signal, the acoustic signal is routed out of the package 38by one or more electrical interconnects through the package 38.

In particular, the bottom face/surface 48 of the package base 40 has anumber of external contacts/bond pads 60 (not shown in FIG. 3, but seeFIG. 5B) for electrically (and physically, in many anticipated uses)connecting the microphone system 17 with an external apparatus. Thisconnection may be a surface mounted connection, or some otherconventional connection. As noted above, the external apparatus mayinclude a printed circuit board or other electrical interconnectapparatus of the next level device (e.g., of a hearing instrument ormobile device). Accordingly, during use, the microphone die 56, andcircuit die 58 cooperate to convert audio signals received within itsinterior into electrical signals, and route those signals throughexternal contacts/bond pads 60 in the base 40 to a circuit board orother external device.

The base 40 and lid 42 may be formed at any of a variety of differenttypes of materials known in the art for this purpose. For example, thebase 40 and lid 42 may be produced primarily from injection moldedplastic. To protect the microphone die 56 from electromagneticinterference, one or both of the base 40 and lid 42 also may haveconductive components. For example, each of the base 40 and lid 42 mayhave a layer of metal on their interior surfaces, or metal integratedinto the interior of their bodies. For example, the base 40 and/or lid42 may be plated with a layer of copper nickel (CuNi). Alternatively,the injection molded material may have embedded conductive particles.Other embodiments may form the base 40 from printed circuit boardmaterial, such as FR-4, ceramic, a carrier substrate, a premoldedleadframe package, or other known structures commonly used for thosepurposes. Like the base 40, the lid 42 also may be formed from othermaterials, such as metal or circuit board material.

Although it may have rounded exterior corners or other minor details(e.g., grooves or bumps), the package 38 is considered to have sixsubstantially planar sides (generally referred to using reference number62) having exterior faces/surfaces (hereinafter “faces”. In particular,those faces 62 include a top face 62A, a bottom face 62B, and four sidefaces 62C and 62D. In the embodiment of FIG. 3, for example, the fourside faces 62C and 62D include two smaller side faces 62C (along thewidth of the package 38) and two larger side faces 62D (along the lengthof the package 38). Each one of these six faces 62A-62D (i.e., thesubstantial majority of their surface areas) is perpendicular to all ofits respective adjoining faces 62, thus forming a rectangular shape asshown in FIG. 3. In other embodiments, however, the package 38 may forma shape other than a rectangle.

The planar exterior surface of one of the smaller side faces 62C definesor forms the above noted inlet port 54, which leads to or forms anopening/mouth 54 (i.e., the above noted inlet port 54) to an acousticchannel 63 that guides this signal to the microphone die 56. Asdiscussed in greater detail below regard to FIG. 5A, this channel 63extends through the base 40 and redirects the incoming acoustic signalto more directly strike the microphone die 56. Of course, discussion ofthe channel 63 extending through the base 40 is but one of manypotential implementations. For example, the channel 63 may extendthrough the base 40 and lid 42 together, or through the lid 42 alone.

In alternative embodiments, the acoustic channel 63 is formed throughone of the other exterior faces 62. Some other embodiments have multipleinlet ports 54 through the same exterior face 62, or through differentexterior faces 62. Accordingly, discussion of the inlet port 54 throughthe smaller side face 62C is not intended to limit all embodiments ofthe invention.

The microphone die 56 may be implemented as any of a number of differenttypes of microphone dies. For example, as suggested above, themicrophone die 56 may be implemented as a MEMS microphone die. To thatend, FIG. 4A schematically shows a top, perspective view of a MEMSmicrophone die 56 that may be used with illustrative embodiments of theinvention. FIG. 4B schematically shows a cross-sectional view of thesame MEMS microphone die 56 across line B-B of FIG. 4A. These twofigures are discussed simply to detail some exemplary components thatmay make up a microphone die 56 that may be used in accordance withvarious embodiments.

As shown in FIGS. 4A and 4B, the microphone die 56 has a chip base 64,one portion of which supports a backplate 66. The microphone die 56 alsoincludes a flexible diaphragm 68 that is suspended by springs 70 over,and movable relative to, the backplate 66. The backplate 66 anddiaphragm 68 together form a variable capacitor. In illustrativeembodiments, the backplate 66 is formed from single crystal silicon(e.g., a part of a silicon-on-insulator wafer), while the diaphragm 68is formed from deposited polysilicon. In other embodiments, however, thebackplate 66 and diaphragm 68 may be formed from different materials.

In the embodiment shown in FIGS. 4A and 4B, the chip base 64 includesthe backplate 66 and other structures, such as a bottom wafer 71 and aburied oxide layer 72 of a silicon-on-insulator (i.e., a SOI) wafer. Aportion of the chip base 64 also forms a backside cavity 74 extendingfrom the bottom of the chip base 64 to the bottom of the backplate 66.To facilitate operation, the backplate 66 has a plurality ofthrough-holes 76 that lead to the backside cavity 74.

In operation, as generally noted above, audio/acoustic signals strikethe diaphragm 68, causing it to vibrate, thus varying the distancebetween the diaphragm 68 and the backplate 66 to produce a changingcapacitance. Such audio signals may contact the microphone die 56 fromany direction. For example, the audio signals may travel upward, firstthrough the backplate 66, and then partially through and against thediaphragm 68. As another example, the audio signals may travel in theopposite direction.

It should be noted that discussion of the specific microphone die 56 isfor illustrative purposes only. Other microphone configurations thus maybe used with illustrative embodiments of the invention. For example,rather than using an SOI wafer, the microphone die 56 may be formed froma bulk silicon wafer substrate, and/or the backplate 66 may be formedfrom a deposited material, such as deposited polysilicon.

Side port microphone systems/packaged microphones known to the inventorsoften have a lower signal-to-noise ratio due to the position of theirmicrophone die relative to their inlet port. Specifically, themicrophone die of such microphone systems typically is mounted to itsbase; namely, orthogonal to the plane of the inlet port. In that case,the acoustic signal does not strike the diaphragm straight on—i.e.,orthogonally. Instead, the acoustic signal of such systems are directedgenerally parallel to the plane of the die and its diaphragm, producinga lower quality signal than desired. In fact, echoes of the acousticsignal can be strong enough to produce a signal-to-noise ratio that isunacceptable in commercially viable systems.

The inventors recognized this problem and, in accordance withillustrative embodiments of the invention, they positioned themicrophone die 56 within the interior chamber 43 at an angle to one ofthe side walls of the package 38. In doing so, they oriented themicrophone die 56 so that it more effectively receives the acousticsignal, producing an improved signal output. It should be noted that theside walls of the package 38 typically include the side walls 44 of thelid 42, as well as some of the thinner side walls of the base 40.

More specifically, FIG. 5A schematically shows a top perspective view ofthe base 40 and the components it supports in accordance withillustrative embodiments of the invention, while FIG. 5B schematicallyshows a bottom view of the package 38. Although FIG. 5A does not showthe lid 42, it should be noted that the lid 42 is removed from thatfigure to highlight features and components within the interior chamber43. Specifically, FIG. 5A more clearly shows the top surface 50 of thebase 40, which has 1) a primary portion 78 that is generally planar andsubstantially parallel to its bottom surface 48, and 2) and a rampedportion 80 that forms an obtuse angle “OB” (FIG. 5D) with the primaryportion 78 and supports the microphone die 56. In addition, the rampedportion 80 also forms the above noted channel 63 that directs theacoustic signal from the input port through the smaller side face 62C ofthe package 38 to the microphone die 56.

The obtuse angle OB formed between the two base regions preferably isgreater than about 90 degrees and less than about 180 degrees. Forexample, the obtuse angle OB can be about 135 degrees, 140 degrees, 145degrees, 150 degrees, etc. . . . . Those skilled in the art can selectthe appropriate angle OB upon a number of design factors, such as thesize and shape of the microphone die 56, and the size of the package 38(particularly the size of the side wall forming the inlet port 54 and,if it forms one, the channel 63). In illustrative embodiments, the angleOB is selected so that the highest edge of the microphone die 56 is veryclosely spaced to the bottom interior surface of the lid 42.

Accordingly, the microphone die 56, which is mounted to the rampedportion 80, naturally is mounted at an angle to the inlet port 54through the smaller side external face 62C of the package 38—i.e., itsbackplate 66 and diaphragm 68 are mounted at an angle relative to theinlet port 54. In illustrative embodiments, this angle is about the sameas that of the ramped portion 80, although some embodiments can bedifferent from the angle of the ramped portion 80. In other words,unlike prior art microphone dies known to the inventors, this microphonedie 56 is not mounted orthogonally or parallel to the inlet port 54.Instead, it is positioned at a non-orthogonal, non-zero angle withregard to the inlet port 54 through the small side face 62C of thepackage 38.

This angle, identified in FIG. 5A as “Angle A,” preferably is less thanninety degrees and greater than about 1-3 degrees. In illustrativeembodiments, Angle A is relatively small, such as on the order of 15-30degrees. One constraint on the size of Angle A is the position of thetop leading edge of the microphone die 56 (identified in FIG. 5A as“Edge E”) relative to the bottom interior surface of the lid 42. Inillustrative embodiments, Edge E either contacts the bottom lid surface(to minimize Angle A), or forms a very small space with the lid interiorsurface to simplify production of the package 38 for tolerance purposes.

The channel 63 formed through the package 38 extends between the inletport/opening 54 and another port/opening in the interior chamber 43 onthe ramped portion 80 of the base 40. As such, the channel 63acoustically couples the microphone die 56 with the inlet port 54. Inillustrative embodiments, the channel 63 has a generally smooth internalcontour (e.g., no sharp turns or interior corners) that directs theacoustic signal in a manner so that much of it substantiallyperpendicularly strikes bottom side of the microphone backplate 66 andeventually the diaphragm 68. As an example, FIG. 4B schematically showsan arrow representing one acoustic signal that (at least a portion ofwhich) should strike the backplate 66 first, and then diaphragm 68 inthis manner.

Accordingly, the channel 63 is configured to cause the incoming acousticsignal to more directly strike the diaphragm 68, improving the responseof the microphone die 56. To that end, as shown in the side view of FIG.5C and the cross-sectional view of FIG. 5D, the channel 63 can have acurvature. In fact, the channel 63 also can have a tapered shape with areducing cross-sectional area from the inlet port 54 to the opposite endof the channel 63. This should help capture the acoustic signal at theport 54, and focus that signal as it is directed toward the microphonedie 56.

Alternative embodiments, however, may form the channel 63 without ataper, and/or without a smooth internal contour. For example, thechannel 63 may have sharp turns, or may direct the signal toward themicrophone die 56 in a manner that does not cause perpendicular signalcontact with the diaphragm 68. Regardless of the channel shape, theseembodiments preferably cause the acoustic signal to strike the bottom ofthe diaphragm 68, thus effectively producing a substantially large backvolume within the interior chamber 43. In some embodiments, rather thanstrike the bottom of the diaphragm 68, some embodiments can direct theacoustic signal to strike the top of the diaphragm 68, thus negating theimproved back volume of the embodiments that strike the bottom of thediaphragm 68.

As noted above, the base 40 preferably is formed from conventionalplastic material. Accordingly, when implemented as being integral withthe base 40, the ramped portion 80 also is formed from plastic materialin the same injection molding process used to form the base 40.Alternative embodiments may form the ramped portion 80 from a componentthat is secured to the base 40. For example, the ramped portion 80 canbe an independently formed plastic, rubber or metal component secured tothe base 40 by a conventional adhesive. As another example, the rampedportion 80 could be an independently formed plastic, rubber or metalcomponent that is coupled with the base 40 using conventional two-shotinjection molding processes.

As noted above, the interior chamber 43 also contains the above notedcircuit die 58. Among other locations, the circuit die 58 may be securedto the primary portion 78 of the base 40, and may include one, two, ormore individual dies. Wire bonds 81 or other interconnect devices canelectrically connect the microphone die 56 with the circuit die 58.

Some embodiments secure the circuit die 58 directly to the top surface50 of the base 40. The embodiment shown in FIG. 5A, however, does notmake such a connection. Instead, this embodiment secures a substrate 82to the primary portion 78 of the base 40, which itself supports thecircuit die 58. Among other things, the substrate 82 may be formed froma circuit board material, such as a flex circuit board.

As shown by FIGS. 5A and 5B, the flexible circuit board 82 in thisembodiment wraps around the base 40, extending from the primary portion78 within the interior chamber 43 to the bottom face 62B of the package38. Accordingly, the flex circuit board provides the necessaryelectrical interconnects from the interior chamber 43 to the exterior ofthe package 38. To that end, the flex circuit board has a plurality ofinternal pads 84 for electrically connecting with the dies, and aplurality of external pads 60 for mounting to an external device (e.g.,a surface mount connection). Alternative embodiments, however, mayprovide electrical interconnects directly through the base 40,terminating at surface mountable pads (or other exterior interconnects,such as pins) on the bottom, top, and/or side faces 62A-62D of thepackage 38. In yet other embodiments, the substrate 82 does not extendoutside of the interior chamber 43.

To facilitate package assembly, the base 40 also has a locationprotrusion 88 at each of its four corners to precisely position the leadon its top surface 50. Each of these protrusions 88 preferably has arounded top surface to more easily make that connection. Accordingly,because they are injected molded parts, the lid 42 and base 40 shouldfit together with small tolerances to produce generally planar exteriorside faces 62C and 62D. It should be noted that minor differences intolerances can produce a small discontinuity with any of the sidesurfaces 62C and 62D and still be within the spirit of variousembodiments. In that case, it is anticipated that although part of theexterior side face 62C or 62D may be on a different plane than anotherpart of its face 62C or 62D, both parts should be generally parallel toform one of the side faces 62C or 62D of the rectangular package 38.

FIG. 6A schematically shows another embodiment of the invention, inwhich the flexible circuit board 82 is oriented so that its externalpads 60 are mounted to one of the side faces 62C or 62D of the package38. FIG. 6B shows that same embodiment without the lid 42 to detail someof the interior features and components. Other than pad placement, thisembodiment shares many of the same characteristics of the embodimentsdescribed above.

FIG. 7 shows a process of forming a packaged microphone, such as one ofthe microphone systems 17 shown in FIGS. 3 and 6A, in accordance withillustrative embodiments of the invention. Although this process isdiscussed in terms of the microphone system 17 of FIG. 3, it can beapplied to other embodiments, such as that shown in FIG. 6A or othersnot explicitly discussed. It should be noted that this process is asimplified version of an actual fabrication process they can have manymore steps. For example, this process may have a testing step, oradditional steps for performing one of the noted steps. In addition,many of the steps of the process can be performed in a different orderthan that disclosed. For example, steps 700 and 702 can be performed ina different order. In fact, some steps can be performed at substantiallythe same time. Accordingly, this process is but one of many differentillustrative processes that may implement various embodiments theinvention.

It also is contemplated that illustrative embodiments of the processwill be performed using batch production processes. In other words, theprocess typically may be completed on a plurality of microphone systems17 at the same time—in parallel. Accordingly, discussion of fabricatinga single microphone system 17 is for simplicity purposes only.

The process begins at step 700, which secures the circuit die 58 to thesubstrate 82 by any of a number of conventional methods. For example,the method may apply a conventional adhesive or die attach epoxy betweenthe bottom of the circuit die 58 and the top of the substrate 82.Alternatively, the circuit die 58 may form a flip-chip connection ontothe substrate 82.

Next, the process secures the substrate 82 with its secured circuit die58 to the primary portion 78 of the base 40, and to the bottom surface48 of the base 40. Again, in a manner similar to the process of securingthe circuit die 58, the substrate 82 may be secured to the base 40 byany of a number of conventional methods, such as using a thermaladhesive, or epoxy tape.

Step 704 then secures the microphone die 56 to the ramped portion 80 ofthe base 40 by any of a number of conventional methods, such as thosedescribed above with regard to the circuit die 58 (e.g., using a dieattach epoxy). In illustrative embodiments, when using the microphonedie 56 shown in FIGS. 4A and 4B, the microphone die 56 is mounted suchthat its backplate 66 and backside cavity 74 are directly adjacent tothe surface of the ramped portion 80. In this case, there are nointervening components between the surface of the ramped portion 80 andthe backside cavity 74.

Acoustic signals therefore pass through the backside cavity 74 andbackplate 66 to contact or strike the diaphragm 68—preferably in anorthogonal manner as described above. Alternatively, the microphone die56 may be configured so that it is mounted with its diaphragm 68directly adjacent to the surface of the ramped portion 80.

After securing both the microphone die 56 and circuit die 58 to the base40, step 706 electrically connects both dies together, and to the base40. Among other ways, the method may use a conventional wire bond 81connecting between the two dies. Alternatively or in addition, each die56 and 58 may have a wire bond 81 connecting to the substrate 82 or someother electrical conductor on the base 40. In yet another embodiment,one or both of the dies are flip-chip connected to the substrate 82.Those skilled in the art can use combinations of these noted electricalconnection techniques, or others conventionally known techniques thatare not discussed, to make the required electrical connections.

At this stage in the process, the base 40 is substantially complete.Accordingly, step 708 couples the lid 42 to the base 40. To that end,conventional processes place the lid 42 onto the base 40 so that thebase location protrusions 88 relatively closely contact the innersurface of the lid walls. More specifically, each location protrusion 88of the base 40 is positioned at one open corner of the lid 42 to providea precise connection with minimal discontinuities on the side exteriorsurfaces 62C and 62D. The location protrusions 88 thus precisely guideand position the lid 42 onto the base 40. Again, as with other steps,conventional techniques may secure the base 40 to the lid 42. Forexample, the process may use a conventional epoxy to connect the lid 42and the base 40.

The substrate 82, which is sandwiched between a portion of the base 40and the lid 42 as it extends between the interior and exterior of thepackage 38, can present a challenge for sealing the interior chamber 43.To meet this design concern, in illustrative embodiments, the lid 42 hasan indented portion to accommodate the extra thickness that thesubstrate 82 adds to the base 40 where it exits the interior chamber 43.Accordingly, the adhesive should sufficiently seal that side of the lid42 against both the base 40 and the substrate 82 to the extentnecessary. In illustrative embodiments, the seal between the base 40 andthe lid 42 is at least sufficient to prevent direct signal access to theinterior chamber 43 other than though the inlet port 54.

Of course, other techniques may connect the lid 42 to the base 40. Forexample, the process may ultrasonically weld the lid 42 to the base 40,and use some additional process to connect and seal the lid 42 and thesubstrate 82.

Accordingly, illustrative embodiments of the invention improve thesignal-to-noise ratio of side port microphones by specially orientingthe microphone die 56 relative to its inlet port 54. This should enablea higher quality output signal within a small form factor forapplications/devices having limited spacing and mounting options, suchas those required by the hearing instruments 10A and 10B.

Although the above discussion discloses various exemplary embodiments ofthe invention, it should be apparent that those skilled in the art canmake various modifications that will achieve some of the advantages ofthe invention without departing from the true scope of the invention.

What is claimed is:
 1. A microphone system comprising: a base having aprimary portion and a ramped portion, the ramped portion forming anobtuse angle “OB” with the primary portion and having a channel; a lidcoupled with the base to form a package with an interior chamber, thepackage having a top, a bottom, and a plurality of sides; a microphonedie positioned within the interior chamber, and being secured to theramped portion; at least one of the sides having a portion with asubstantially planar surface forming an opening for receiving anacoustic signal, the channel being acoustically coupled with the openingand guiding the acoustic signal therethrough, the acoustic signal makingcontact with the microphone die orthogonally; the microphone die beingpositioned at a non-orthogonal, non-zero angle with regard to theopening in the at least one side.
 2. The microphone system as defined byclaim 1 wherein the microphone die has a diaphragm, the channel furthercomprising a contour that is configured to direct the acoustic signal ina direction that is substantially orthogonal to the diaphragm.
 3. Themicrophone system as defined by claim 1 further comprising a substratesecured with the base, the substrate supporting a circuit die.
 4. Themicrophone system as defined by claim 3 further comprising a wire bondelectrically connecting the microphone die with the circuit die.
 5. Themicrophone system as defined by claim 1 wherein the base includes atleast one location protrusion, the at least one location protrusionbeing positioned adjacent to the lid.
 6. The microphone system asdefined by claim 1 further comprising a device housing configured forconnection with a person's ear, a speaker within the housing, andcontrols for controlling the microphone die and speaker.
 7. Themicrophone system as defined by claim 1 wherein one or both of the baseand lid include injection molded material and conductive material tomitigate electromagnetic interference.
 8. The microphone system asdefined by claim 1 wherein the package has a plurality of external sidefaces, the microphone die being positioned at a non-orthogonal, non-zeroangle with regard to the plurality of external side faces.
 9. Amicrophone system comprising: a base having a primary portion and aramped portion, the ramped portion forming an obtuse angle “OB” with theprimary portion and having a channel; a lid coupled with the base toform a package having an interior chamber, the package having aplurality of exterior sides that together form a generally rectangularexterior shape; an opening formed through one of the exterior sides ofthe package and responsive to an acoustic signal, the openingacoustically coupling the interior chamber with the exterior of thepackage; and a MEMS microphone die mounted within the interior chamberthe MEMS microphone die being mounted within the interior chamber at anon-orthogonal, non-zero angle to the opening and secured to the rampedportion, the channel guiding the acoustic signal therethrough, theacoustic signal making contact with the MEMS microphone dieorthogonally.
 10. The microphone system as defined by claim 9 furthercomprising a substrate secured with the base, the substrate supporting acircuit die in electrical communication with the MEMS microphone die.11. The microphone system as defined by claim 10 further comprising awire bond electrically connecting the MEMS microphone die with thecircuit die.
 12. The microphone system as defined by claim 10 whereinthe substrate extends to the exterior of the package, the substratehaving a first pad for surface mounting with an external device, thesubstrate having a second pad for electrically connecting with thecircuit die within the interior chamber.
 13. A method of forming amicrophone system, the method comprising: providing a base having aprimary portion and a ramped portion, the ramped portion forming anobtuse angle “OB” with the primary portion and having a channel;providing a lid; securing a microphone die to one of the ramped portionof the base and the lid; and securing the base to the lid to form apackage having an interior chamber containing the microphone die, thepackage having a plurality of exterior sides that together form agenerally rectangular exterior shape, at least one of the plurality ofexterior sides forming an opening for receiving an acoustic signal intothe interior chamber, the microphone die being positioned within theinterior chamber at a non-orthogonal, non-zero angle to at least one ofthe exterior sides, the channel guiding the acoustic signaltherethrough, the acoustic signal making contact with the microphone dieorthogonally.
 14. The method as defined by claim 13 wherein the baseincludes a plurality of location protrusions, the lid having a top walland a plurality of side walls extending from the top wall, securingcomprising positioning the side walls around the plurality of locationprotrusions to locate the location protrusions within the interiorchamber.
 15. The method as defined by claim 13 further comprisingsecuring a substrate to the base, the substrate extending from withinthe interior chamber and exterior to the interior chamber, the methodalso securing a circuit die to the substrate.
 16. The method as definedby claim 13 wherein the lid comprises plastic and a layer of metalmaterial to mitigate electromagnetic interference.
 17. The method asdefined by claim 13 further comprising mounting a circuit die within theinterior chamber, the method further securing a wire bond to themicrophone die to electrically connect the microphone die with thecircuit die.